Blisters are caused by abrasion against the skin. Lubicating the skin can keep that abrasion from causing blisters. The lubricant you use should be one that will last for the length of your walk. Apply any lubricant liberally to your feet in any area that is prone to blistering.
1. Vaseline Petroleum Jelly
It's cheap and it works. I put great gobs of petroleum jelly on my feet before I put on my Cool-Max socks. No blisters, not even on a marathon - and I used to get big heel blisters every time at 10 miles. No, my feet don't slide around in my shoes - the socks prevent that. No, it doesn't feel slimy once you put on your socks. It doesn't wash out well but who cares - these are walking socks! Use the plain petroleum jelly, not any of the fancy cream versions.
2. BodyGlide
A no-petroleum stick that goes on like a deodorant stick. It won't stain your clothing. It comes in regular and a version that includes sunscreen. Good for preventing blisters on your feet. I use this by itself for 6-10 miles walks and put it on first, before the petroleum jelly, for longer distances.3. BlisterShield
Blistershield comes in two varieties. One is a silicone-based roll-on that provides long lasting lubrication to prevent blisters and chafing. It is odorless, non-greasy. The second variety is powdered silicone to put into your socks to help prevent blisters.4. SportSlick
Think of it as high-tech petroleum jelly. It combines silicone, polymers, and petroleum jelly for long-lasting waterproof lubrication. Includes aloe, antioxidant vitamins E and C, natural plant extracts, Tolnaftate antifungal agent and Triclosan antibacterial agent.5. Hydropel
Endorsed by ultra-distance athletes and triathletes, this high-tech lubricant can keep you from getting rubbed the wrong way.6. Squeaky Cheeks Performance Powder
or chafing and for foot blister prevention, Squeaky Cheeks is a cornstarch and essential oils solution for those who don't want to mess with greasy preparations.7. Band-Aid Blister Block Stick
This convenient stick uses vegetable oil as its lubricant. Just rub on your feet and go.